EP 0 701 014 B1 (U.S. Pat. No. 5,626,011) discloses an apparatus for producing a twist yarn in an integrated open end spinning and twisting process. The apparatus includes a rotatably driven spindle rotor mounted to a machine frame and having a spindle hollow axle that is communicated with a substantially radially outwardly extending yarn guide channel. A yarn traveling outwardly of the yarn guide channel is guided by a balloon limiting device to a centering eye located at an axial extension of the spindle hollow axis and the yarn is thereafter wound on a winding package. Within the area circumscribed by the rotating balloon limiting device, two upwardly opening spinning rotors are supported in side-by-side relationship above the spindle rotor symmetrical to the spindle hollow axis, and fiber material is fed through the yarn balloon to the spinning rotors. The spun yarn produced by the spinning rotors is drawn out of the spinning rotors in a yarn withdrawal direction and guided into a 180xc2x0 reverse direction to enter into the spindle hollow axle for passage therethrough as noted above in connection with the twisting of the yarn according to the two-for-one principle.
To produce the spun yarn, it is necessary to dispose a joining strand or thread in each spinning rotor. EP 0 701 014 B1 discloses a corresponding method and apparatus for effecting this process of disposing a joining thread in a spinning rotor.
Certain disadvantages are incurred in the use of the joining thread disposition process as described in EP 0 701 014 B1 in the course of an integrated open end spinning and twisting process in that there may be a relatively long extent of the yarn which extends from the joining thread portion of the yarn in which the yarn strands or threads are not twisted with one another. Under certain conditions, this may result in the entire twist yarn package being unusable for further textile operations. This undesired occurrence of such a relatively long extent of untwisted yarn may occur as well in the event of a yarn break.
The present invention provides a method for spinning fibers onto the free ends of the two threads of a yarn which is produced during an integrated spinning and twisting process and a two-for-one spinning and twisting apparatus for performing the method such that, immediately after the commencement of the spinning process, the twisted yarn which is produced exhibits no extent of non-twisted yarn or, at most, only a very short extent of non-twisted yarn.
In the implementation of the method of the present invention, the clamping of the individual threads, which involves clamping a thread loop formed from the yarn extending from the spindle hollow axle and having a first branch of the thread loop extending into a spinning rotor and a second branch extending into the spindle hollow axle, ensures that the twist imparted to the spun yarn by the open end spinning process is maintained, whereby a curling of the spun yarn in the area of the thread loop is prevented.
The twist imparted by the open end spinning process can only become undone along the yarn over a relatively short end portion thereofxe2x80x94namely, in that portion of the spun yarn which lies between the clamping location of the thread loop and the free end of the first branch of the thread loop which has been disposed in the spinning rotor. This free thread end is typically inserted sufficiently into the spinning rotor so as to ensure that, at the commencement of the feed of fiber material into the spinning rotor, the free thread end is at a spacing from the fiber collecting rim of the spinning rotor and continues to remain in the spinning rotor in spite of the centrifugal force applied thereto due to the spinning of the spinning rotor.
If sufficient fiber material is fed into the spinning rotor during a spinning operation, then a spin joining process will occur in which the first branch of the thread loop which had been inserted into the spinning rotor is joined by the fiber material and, in connection with this operation, the further drawing in of the second loop branch into the spindle hollow axle due to the commencement of the winding operation leads to the dissolution of the thread loop, whereby those free ends of the threads in the spinning rotors which were formerly the first branches of the thread loops and the spun fibers which have been joined therewith by the spinning operation are drawn into the spindle hollow axle and are thereafter followed by spun yarn produced by the spinning rotors, and twist is imparted to the thus formed yarn by the two-for-one spinning and twisting apparatus.
At the commencement of the open end spinning operation during which the free end of the one threadxe2x80x94i.e., the first branch of the thread loopxe2x80x94is disposed in the spinning rotor, a spin direction is imparted to the free thread end by the spinning rotor, whereby, immediately following the spin joining operations in the two spinning rotors, the two threads having the required spin direction for the subsequent two-for-one twisting operation are now available.
The disposition of the free thread ends into the individual spinning rotor or, respectively, its fiber collecting rim can be additionally facilitated by the clamping of the thread loopxe2x80x94that is, the clamping of the first and second branches of the thread loop between the stationary and movable clamp platesxe2x80x94and the passage of the first and second branches of the thread loop through the nip of the set of rollers of the delivery device, whereby the first branch of the thread loop is guided into the spinning rotor and the second branch of the thread loop is guided into the spindle hollow axle.
If during the spin joining operation, which begins after the commencement of the winding operation, the twisting of the yarn in the two-for-one twisting process begins, the two threads, whose free ends in the spinning rotors will have fiber material joined thereto, are drawn into the spindle hollow axle, whereby the rollers of the delivery devices are positively set into rotation so as to facilitate the delivery of the free thread ends into the spinning rotors.